The apron is perhaps the most symbolically important emblem found in speculative
Masonry. It is made of pure white lambskin and is worn by every Mason to
all Lodge events. The apron is the first symbol explained to the Entered
Apprentice (1st degree, Blue Lodge) and the first tangible evidence that he
possesses of his admission into the fraternity. What the Mason probably
doesn't know at the time of his initiation is that the apron is also worn by
temple Mormons and active practitioners of Wicca (witchcraft).
The Mason is taught that the apron is an "emblem of innocence and the badge
of a Mason." According to Joseph Fort Newton, author of The Words
of a Great Masonic Divine, "…'by the lambskin,' the Mason is
reminded of the purity of life and rectitude of conduct which is so essentially necessary
to his gaining admission into the Celestial Lodge above, where the Supreme
Architect of the Universe presides." 1

In the Mormon temple ceremony, the participant is presented with a green satin
"fig leaf" apron. In the "Garden of Eden" portion of the
ceremony, the character portraying Adam asks Lucifer, "What is that
apron you have on?" Lucifer answers, "It is an
emblem of my power and Priesthoods." 2 Participants
obediently follow the narrator's voice as he directs them to put on the apron
that has already been explained to them twice as an emblem of Lucifer!

According to William Schnoebelen (former Mormon, Mason, and Witch; author of Mormonism's
Temple of Doom), "...in magick, the apron is a symbol of magickal
energy or planetary (astrological) force. It is the badge or rank for the
third degree; and represents (when green) the priestly office of Lucifer. It
is the magickal 'tool' of that degree.

"In this third degree of Wicca, the apron serves a practical, magickal
purpose. In this degree, through a bizarre ceremony called the Great Rite,
one is initiated into the principle of sex magick (tantra yoga). The apron
is often used during this sort of ritual to help contain and channel sexual
energy. This is why it covers the genital area....it serves rather like
putting a lid on a teakettle to help bring it to a boil. This channeling
raises the Kundalini force and supposedly produces enlightenment when the
Kundalini serpent strikes upwards and 'bites' you metaphysically at the base of
the brain.

"...just as the stole is the emblem of authority in the Catholic
Priesthood, so the green apron is the emblem of Lucifer's authority. In
every Satanic group I knew of, the hierophant (High Priest) always wore a green
apron, usually of the finest silk or satin." 3

Schnoebelen gives this conclusion of the Mormon ceremony and use of the apron, "...as
I saw Lucifer with his Priesthood apron—and as I received my own apron—I was
convinced that Christianity reached its highest level of witchcraft in
Mormonism. Jesus, I had been taught as a witch, was a Medium of the
highest order, who worked miracles by magick. Now as I saw the priesthood
of Lucifer transferred to Adam in the Apron, I knew it was true." 4

References:

(1) Joseph Fort Newton, The Words of a Great Masonic Divine, p. 4 (found
in the introductory section of the 1957 edition of the Masonic Bible)